Propellent powder



Patented DecVZQ), 19311 serene RICHARD GEORGE WOODBRIDGE, OF WILMINGTON,DELAWARE, ASSIGNOR TO E. I. DU POINT DE NEMO'URS & COMPANY, OFWILMINGTON, DELAWARE, A CORPORATION OF DELAWARE No Drawing.

7 This invention relates to a fiashless propellent powder and moreparticularly to a flashless propellent powder of the nitrocellulosetype.

This case is a continuation in part of my copending application SerialNumber 81,086, filed January 13,1926.

Dautriche, Comptes Rendus 1908, volume 146, pages 535-538, disclosedthat the use of sodium and potassium salts, particularly saltpetre(potassium nitrate), prevented the ignition of fire damp in mines whenused in small amounts, 3 to 6%, in explosives having an ammonium nitratebase. Dautriche in the same article cited-the use of salts of sodium andpotassium for the suppression of muzzle flash and of the recurrence offlame (flare back) in the firing of smokeless powder.

Vennin and Chesneau Les Poudres et Explosifs et Les Mesures de.Securitedans les Mines de Houille (published in 1914) discusses at considerablelength the influence of alkaline salts in explosives and smokelesspowder for suppression of flash as follows:

Page 139, section 107-Influence of alkaline salts. 1

Page 158, section 123-Flare back.

Page 318, section 300Volatilizable salts and alkaline salts.

Page 445, section 419-Flash and flare back.

Page 445, section 420.

According to Vennin and Chesneau, page 445, section 420, above,Dautriche also appreciated that the saltpetre content of the blackpowder making up the priming char e also acted to suppress flash, aswill be 0 served from the following:

The addition of alkaline salts to the charge gives'us much greatersafety as it almost always causes the gas to be extinguished (DautricheComptes Rendus 1908, volume 146, page 537). The experiments made by M.Dautriche in this connection have also shown that the primin charge ofblack powder reduces considera ly, but not entirely, the probability offlare back.

p The use of saltpetre, or other sodium or potassium salts forextinguishing muzzle flash in guns, has not found general use inApplication filed April 13,

1928. .Serial No. 269,881.

military propellants, due to a number of factors. According to Marshall,Explosives, (year 1915) page 246, I The quantity of smoke is therebyincreased and this will reveal the position by day, and will obstructthe gunmen. Marshall, in A Short Account of Explosives (year 1917) page96, states The flame can be diminished by the addition of a coolingagent to the powder or a small proportion of a salt of sodium orpotassium, but these additions are liable to increase the amount ofsmoke, which is equally objectionable, especially by day.

Another objection to the use of salts of sodium and potassium for theprevention of muzzle flash, is that many of these salts are seriouslyhygroscopic. Edwards, British Patent Number12,188 of 1908, states Ithaslong been suggested that this result (prevento decompose under theinfluence of hygrometric variation, and to become deliquescent insidethe substance of the explosive itself in which they have been embodied,and consequently to bring about the more or less rapid and more or lessdangerous decomposition of the explosive.

Another and serious objection to the use of salts of sodium andpotassium for the pre vention of muzzle flash, is that military cannonpowders of the nitrocellulose type have for many years, and particularlyduring the World War, been water dried, that is, treated in hot water toremove more rapidly the volatile solvents, ether and alcohol, used intheir manufacture. Sodium and potassium salts which appear to possessthe special property of preventing muzzle flash, are readily s olu blein water, particularly in hot water, so that it would be expected thatsalts of potassium and sodium would be readily removed from thenitrocellulose colloid if the same were subjected to a. water dryingtreatment. I

It is known that Germany, during the World War, made use of packets ofpotassium chloride which were added to the powder charge, largely atnight, for the prevention of muzzle flash. It is also known that suchadditions seriously disturbed the ballistics of the powder charge asrelatively large amounts of potassium chloride were required.

German Patent No. 301,659, issued May 14, 1921, discloses that the use.of small amounts of potassium chloride when added tosmokeless powderwill prevent the occurrence of muzzle flash. Paragraph 4, firstsentence, of this patent states as follows:

With all nitrocellulose powders, and with powders containingnitrocellulose and nitroglycerine for guns of small caliber, smalladditions of potassium chloride of 0.5 to 2% suflice; on the other hand,with nitrocellulose-nitroglycerine powders of high combustiontemperatures for larger guns, amounts of 3 to 5% are necessary. 4

In my copending application No. 81,086, filed January 13, 1926, I haveshown that flashless results can be obtained in small guns such as the75 m/m field gun, model 1897, with a propellent powder of the followingcomposition 85 parts nitrocellulose of about 13.15% nitrogen 10 partsdinitrotoluol 5 parts dibutylphthalate 1% added diphenylamine and withother similar compositions in which dimethyldiphenylurea, acetyllaurins, ethyl palmitate, diethylphthalate, and dibutyltartrate aresubstituted for the dibutylphthalate. However, the compositioncontaining the dibutylphthalate is the preferred composition.

In larger guns such as the 155 m/m G. P. F. gun I disclose in my saidcopending application that it is necessary to increase the amount ofdibutylphthalate to about 10 parts, decreasing the amount ofnitrocellulose from 85 to 80 parts in order to obtain flashless results,but that elimination of the luminous muzzle flash in this manner givesrise tomore smoke.

The manufacture and testing of propellent powders for guns requiresconsiderable time and large expenditures, but it is only by such testingthat claims for an improved propellant can be substantiated. The factthat a powder givesflashless results in one gun does not necessarilymean that the same composition or a different combination of the sameingredients, will give fiashless results in all guns. Furthermore,flashless results mean little or nothing if the same are not accompaniedby the desired or standard ballistics far the particular gun, togetherwith an acceptable uniformity in Velocity and pressure with an amount ofsmoke which is acceptable to the user of the powder, besidessatisfactory chemical stability as well as ballistic stability of thepowder.

I have found as a result of actual experiments covering a period ofyears that flashless results with the required standard ballistics andwithout an objectionable amount of smoke, can be readily obtained in anumher of the smaller guns, including the 2.95

inch mountain gun, 75 m/m pack howitzer,

75 m/m field gun, model 1897, 75 m/m field gun, model 1920 (normalcharge), and 105 m/m howitzer with powder of the composition 85 partsnitrocellulose of about 13.15% nitrogen 10 parts dinitrotoluene 5 partsdibutylphthalate 1% added diphenylamine.

Also that similar satisfactory results are obtained in the 75 m/m fieldgun, model 1920 (super charge) and in the 3-inch anti-air craft gun,model 1917, with 15-pound projectile with powder of the composition 83parts nitrocellulose of about 13.15% nitrogen 10 parts dinitrotoluene 7parts dibutylphtha-late 1% added diphenylamine.

increased amount of. smoke; in other gunsand for other uses, the amountof smoke is a serious disadvantage. It is also obvious that a powderwhich may give oil an objectionable amount of smoke in the day-time maybe entirely satisfactory for night firings. I have therefore, continuedexperiments with the object of obtaining flashless results with reducedamount of smoke in the more difiicult guns, especially the larger guns.

The object of my invention is to produce a smokeless propellent powderfrom nitrocellulose without the aid of nitroglycerine, which willpossess greatly reduced hygroscopic qualities as compared with powdermade from nitrocellulose only. A further object of my invention is theelimination of the white luminous flash such as is produced at themuzzle of guns, for example, by the present Pyro Service Powder of theUnited States Government. This white luminous muzzle flash is commonlyattributed to the ignition of the combustible gases formed during thecon ibustion of smokeless powders, due

ide, carbon monoxide, hydrogen, water vapor and small .amounts ofmethane. Of these, the combustible gases are carbon monoxide,

hydrogen and methane. The white luminous flash at the muzzle of the gunis due to the combustion of these gases in the presence of oxygen. Thiscombustion can be prevented in the case of small arms by firing into anatmosphere of carbon dioxide. When the White luminous flash iseliminated in this manner, or is eliminated by the use of a pow-.

der containing suitable ingredients, only a small reddish glow appearsat the muzzle of the gun. This glow is not readily visible and can beeasily concealed.

A further object of my invention is the production of a nitrocellulosepropellent powder which, besides being of greatly reduced hygroscopicityand flashless in most guns, can be dried not onlyin air but also in hotwater to more effectively and expeditiously remove the volatile solventsadded for the purpose of assisting in the colloiding of thenitrocellulose.

A still further object of my invention is to retain as far as possible,the advantages of the improved propellent powder as described in mycopending application, aforesaid, therefore only modifying itscomposition to the slightest degree necessary in order to obtainflashless results in certain guns in which flashless results orconsistently flash less results are not readily obtained withouexcessive amounts of black smoke.

Other objects will appear as the descrip tion proceeds.

These objects are accomplished by incorporating in the powder an alkalisalt that is non-hygroscopic up to about 90% relative humidity atatmospheric temperatures and that has no harmful action on the stabilityof the powder. q I

For example, I have obtained consistently flashless results in the3-inch anti-air craft gun, model 1917, with the 12.7 pound projectileand with only the smallest amount of whitish to whitish gray smoke withpowder of the following composition:

85 parts nitrocellulose of about 13.15% nitrogen content 10 partsdinitrotoluene 5 parts dibutylphthalate 1 part diphenylamine r 1 partpotassium sulphate.

I have also found that the above powder gives complete and consistentlyflashless rewhereas flashless results are only obtained with powder ofthe composition:

82 parts nitrocellulose of 13.15% nitrogen '10 parts dinitrotoluene 8parts dibutylphthalate 1 part diphenylamine by the use of an extraignition charge of about 5 ounces of black powder placed preferably atthe front, end of the powder charge. In the latter case, while flashlessresults are usually obtained, the amount of smoke is considerable andthe color medium to dark I have found that approximately 1% of potassiumsulphate in the above composition can be replaced by an equal amount of.po-

tassium nitrate, potassium phthalate, sodiumnitrate and sodium chloride.Salts which I have found do not give flashless results or consistentlyso, include calcium phthalate, lead phthalate, strontium phthalate,calcium oxalate, barium sulphate, lead sulphate and calcium sulphate,and also potassium chloride when added in the same amount as potassiumsulphate in the above formula.

Of the salts of sodium and potassium which I have found give flashlessresults, I prefer to use those which are non-hygroscopic up to about 90%relative humidity at atmospheric temperatures and also which have noharmful action on the stability of the powder. For example, I have foundthat sodium nitrate, and potassium phthalate are, too bygroscopic to besuitable for use as an ingredient of a military propellent powder togive the most satisfactory results. Also sodium chloride in addition tobeing too hygroscopic, will blacken powder containing di- .phenylamine,which discoloration is very obj ectionable, indicating harmful action onthe stability of the powder. Potassium chloride is open to the sameobjection of blackening the powder even if this salt had given equallysatisfactory results as regards suppression of flash.

Of the salts tried, I have found that potassium sulphate and potassiumnitrate are the most satisfactory, so far as obtaining I 3-inchanti-aircraft gun, model 1917, with the 12.7 pound projectile: 85 partsnitrocellulose of about 13.15% nitrogen 10 parts dinitrotoluene 5 partsdibutylphthalate 1 part diphenylamine 1 part potassium sulphate orpotassium ni trate.

In the ignition of the above powder there was used the regular ignitioncharge as used for propellent powder of the Pyro type, in the 155 m/m G.P. F.'gun, namely a 21 gram two compositions made up for the 3-inchanti-aircraft gun, model 1917, and 'fired with the 12.7 pound proof slugwith regular 110 grain primer.

Potas- Percentslum Mean g fi i Muzzle pressure 51 Composition of powdersulphate finighed g figyg gg Muzzle flash and smoke in p r. powderplatinic g g fi as made chloride method 8% pigs. dN/Cf13t.1]5%1N. 1 s.ini r 0 no p ts. dibutylphthalate. 0. 98% 0. 84% 5 lbs. 2693 28050 Noflash and medium white smoke. 1 pt. diphenylamine. 1 pt potas. sulphate.

85 pts. N/C 13.15% N. pts. dinitrotoluol. 5 pts. dibutylphthalate. 2.41% 2. 5 lbs. 2727 30070 No flash and medium white smoke. 1 pt.diphenylamine. 3 oz. 2.5 pts. potas. sulphate.

Pyro Service Powder. None. None. 10 8% lbs. 2703 28540 Large flash.

primer with an 8 ounce ad of black powder at the base of the pow ercharge. As black powder contains about 75% of saltpetre, the 8 ounces ofblack powder would contain 6 ounces of saltpetre. When muzzle flash isobtained with-the ordinary powder this saith petre is volatilized by theflash. \Vhen the muzzle flash is prevented as by the addition of 1%potassium sulphate in the powder, this six ounces of saltpetre is thecause of a certain amount of white smoke due to finely divided particlesof potassium carbonate and potassium sulphate caused by the combustionof the black ignition powder. This white smoke in the present examplewould be increased by the smoke from about four ounces of potassiumsulphate or the amount present in the 25 pound required weight of chargeof powder containing about 1% of potassium sulphate. While occasionalflashless results can be obtained with powder of the above compositioncontaining 0.50% and 0.75% potassium sulphate instead of about 1.0%, themargin of safety as regards flashlessness is seriously reduced therebyand besides the amount of white smoke is reduced only by the smallreduction in the amount of potassium sulphate in the powder as the eightounces of black ignition powder is fixed and required for the ignitionof the powder charge.

In view of the high solubility of potassium sulphate in water, thepowders containing this salt were first air dried for both the 3- inchanti-aircraft gun, model 1917, and the 155 m/m GI P. F. gun. However, Ihave discovered. that powder of the above composition conta-ining 1% ofpotassium sulphate can be water dried with so little loss of thepotassium sul hate that nospecial m caution need be taken in the watertreat ment of the powder to prevent or minimize the extraction'of thesalt. For example, the

I following table gives the results obtained on The above powderscontaining potassium sulphate were subjected, after solvent recoverytreatment to recover ether and alcohol used in their manufacture, to awater drying treatment, that is, steeping in hot water at 55 C. for sixdays with frequent changes in water. The loss of potassium sulphate wasvery small. On the other'hand potassium nitrate appears to be morereadily removed from the powder during the water drying treatment, butless so than from an etheralcohol nitrocellulose powder withoutadditions of non-volatile, water-insoluble nitrocellulose solvent suchas dinitrotoluene and dibutylphthalate. This difficulty of removingpotassium sulphate and to somewhat a lesser degree, potassium nitratefrom my powder, may be due to the fact that the mixture of dinitrotoluoland, dibutylphthalate both of which are solvents for nitrocellulose,give a more thoroughly colloided powder than an ether-alchol colloid ofthe same nitrocellulose without additions of dinitros toluol anddibutylphthalate, the ether-alcohol colloids only the soluble and notthe insoluble nitrocellulose, while the mixture of dinitrotoluol anddibutylphthalate colloids both the soluble and insoluble types ofnitrocellulose durin the process of manufacture. Thus the discovery thatpotassium sulphate when used in my composition is not readily extractedfrom the powder during the water drying treatment, is a very importantone, as large economies in time and money are possible when thepropellent powder can be water dried as against the air discolor the 10white smoke to that which would normally be produced from the blackpowder contained in the primer or the ignition pad. The potassiumsulphate has no harmful effect. on the chemical stability and does notpowder as does potassium chloride. I have experimented with potassiumsulphate by the addition of packets of this material contained in silkbags to the powder charge. I have found that by the use of a largerquantity of potassium sulphate than is required when uniformlyincorporated in the powder, flashless results are frequently obtained,but on account of the larger amount of potassium sulphate "used, the'quantity of white smoke is appreciably increased, and the ballistics ofthe powder disturbed. It is therefore obvious that the small quantity ofpotassium sulphate which, when incorporated in the powder preventsmuzzle flash, is due to the fact that the salt is uniformly distributedthroughout the powder. It is therefore obvious that in cases where it ispreferred not to incorporate potassium sulphate in the powder, but touse it by adding it to the powder charge, that better results arepossible by more uniformly distributing the potassium sulphatethroughout the charge such as by using silk weighted with the salt ornitrocellulose, cellulose ester or other films in which the salt hasbeen incorporated. However, I prefer to incorporate the potassiumsulphate in the powder, in orderto simplify the loading of the powderand the use of the loaded charges.

The manufacture of the powder requires no special skill. Thenitrocellulose is dehydrated with denatured ethyl-alcohol of suitablegrade and then colloided in asuitable mixer with the addition of ether.There is added in the ether or directly to the mixer, the dinitrotolueneand the dibutylphthalate.

Due to the solvent action of the latter two ingredients, less alcoholand ether are required than are usually employed for nitrocellulosepowders not containing these ingredients. The potassium sulphate isuniformly and finely ground in a ball mill or other type of mill to afineness sufficient to passthrough a wire screen with meshes to theinch. However, I do not limit myself to-this fineness. Diphenylamine isusually added as a stabilizer and is usually dissolved in the ether. Thecolloid may be pressed either in tubular grains with one or moreperforations or in the solid grain, or in the ribbon or strip form ofgrain. The grains of powder are given thorough solvent recov erytreatment before the final drying, which may be in air or hot water at atemperature not in excess of 60 C. although a higher temperature may beused without injury to the chemical stability of the powder.

While I prefer to use a standard composition containing partsnitrocellulose of about 13.15% nitroen. '10 parts dinitrotoluol 5 partsdibutylphthalate 1 part diphenylamine 1 part potassium sulphate it willbe understood that I do not limit myself to these proportions or tothese ingredients. For example, the nitrocellulose may be of a mixtureof the type soluble in ether-alcohol with the type insoluble inetheralcohol mixture (two parts ether to one part ethyl-alcohol) and ofahigher or lower nitrogen content than 13.15% or it may be entirely ofthe soluble type, having a nitrogen content between about 12.0 and about12.80%.

The dinitrotoluol may be decreased or increased or replaced by othernitro compounds.

The dibutylphthalate may also be increased or decreased or entirelyomitted, or replaced by other "cooling agents which'are solvents fornitrocellulose such as those mentioned in the foregoing and in mycopending application aforesaid.

The amount of potassium sulphate which I prefer to use will -be in theneighborhood of 1%, but it will be understood that it is added merelyfor the purpose of preventing muzzle flash to a composition flashless inmany guns and approaching flashlessness in other guns.

Therefore, the minimum quantity required to prevent flashmay be as lowas 0.50%. I prefer not to add more than 2.0% in order to obtain theminimum amount of white smoke.

While I prefer to use potassium sulphate as an ingredient of powder ofthe nitrocellulose type, that is, without nitroglycerine, on account ofthe recognized lower erosion caused by nitrocellulose powders ascompared with nitroglycerine, I do not intend to be limited in my claimsto powders of the nitrocellulose type. It is obvious that the flashpreventing properties of the potassium sulphate are equally applicableto all propellent powders, regardless of the composition. Furthermore,in powders of the nitroglycerine type having a high temperature ofcombustion, an increased amount of potassium sulphate will be requiredto prevent muzzle flash unless the temperature of combustion of thenitroglycerine powder is reduced by the use of Vaseline, carbon,methylethyldiphenylurea or diethyldiphenylurea or ders, it is preferredto air dry the powder,

since there is serious loss of nitroglycerine during hot water steepingof powder containing this ingredient. I

The invention is applicable to the production of flashless powder forsmall arms and cannon.

Some of the advantages of my flashless powder over other powders arebriefly as follows:

Flashless results are obtained by the uniform incorporation in thepowder of relative ly finely pulverized potassium sulphate. Due to thefact that the composition of 85 parts nitrocellulose of about 13.15%nitrogen content. 10 parts dinitrotoluol,

5 parts dibutylphthalate 1 part diphenylamine gives flashless results inmany of the smaller guns, and tends to approach fiashlessness in otherguns, a less quantity of potassium sulphate is required than wouldotherwise be the case, which results in flashlessness being obtained.with less smoke than if a larger -quan tity were required.

Powder of the above type containing potassium sulphate may be dried bysteeping in hot water without removing any substantial amount of thesalt.

Potassium sulphate is less hygroscopic than the saltpetre or potassiumnitrate used in the black -powder ignition charge so that the powder canbe subjected to humidity conditions up to and above 93% relativehumidity, at which relative humidity potassium nitrate will deliquesce,without change other than slight increase in moisture, due to the higherhumidity condition. Potassium sulphate is not hygroscopic until about97% relative humidity.

Potassium sulphate does not discolor powders containing diphenylamineand is without harmful effect on the stability of powder.

As many apparently widely different embodiments of this invention may bemade without departing from the spirit thereof, it is to be understoodthat I do not intend to limit myself to the specific embodiments thereofexcept as indicated in the appended claims.

I claim:

1. A propellent powder comprising nitrocellulose in combination with adeterrent eX- plosive and deterrent material, each of which whenin-liquid form has a substantial solvent action on the nitrocellulose,and a muzzle flash eliminator comprising potassium sulphate.

2. A propellent powder comprising nitrocellulose in combination withsubstances which when in liquid form have a substan tial solvent actionon the nitrocellulose, said substances comprising nitro-aromaticcompounds, and a cooling agent, and a muzzle flash eliminator comprislngpotassium sulphate.

3. A gelatanized nitrocellulose propellent powder containing a muzzleflash preventative which comprises potassium sulphate.

4. A gelatinized nitrocellulose propellent powder containing a muzzleflash preventative which comprises 0.5 to 2.0 per cent of potassiumsulphate.

5. A propellent powder. comprising nitro cellulose, a polynitrotoluene,a dialkylphthalate, and potassium sulphate.

6. A propellent powder comprising nitrocellulose, a polynitrotoluene, adialkylphthalate, and 0.5 to 2.0 per cent potassium sul- 10. Apropellent powder containing as an ingredient, potassium sulphate.

11. A propellent powder containing as ingredients, nitroglycerine and asmall quantity of potassium sulphate.

12. A propellent powder containing as ingredients, nitrocellulose,nitroglycerine, and

a small quantity of potassium sulphate.

13. A propellent powder containing as an ingredient, 0.5 to 2.0 per centpotassium sulphate.

1 1. A propellent powder containing as ingredients, nitroglycerine and.5 to 5.0 per cent potassium sulphate.

15. A propellent powder containing as ingredients, nitrocellulose,nitroglycerine, and .5 to 5.0 per cent potassium sulphate.

16. A propellent powder charge containing a muzzle flash preventativecomprising potassium sulphate.

In testimony whereof, I aflix my signature.

RICHARD GEORGE WOODBRIDGE.

